For the purpose of improving the transfer efficiency, the coil unit used in a wireless power supply system is composed of a magnetic body in order to increase the coupling coefficient between the coil unit for power transmission and the coil unit for power reception. When the magnetic body is composed by ceramic material, its mechanical stress is quite weak due to its hardness and fragility, and cracks would be produced once a certain impact is applied, and thus special attentions should be paid.
For such a requirement, Patent Document 1 has disclosed that the ferrite layer which is divided into ferrite sheets, the longest side of which is ten times or less as long as that of thickness, has been sufficiently divided so that it can be prevented from being further divided even a stress is applied when it is being mounted or after it is mounted.